Fig. 3.

Block of D172N Kir2.1 current by intracellular chloroquine is voltage-dependent. A, Effect of intracellular application of chloroquine on D172N Kir2.1 current recorded in excised inside-out patches. Currents from a single cell elicited by 1 s step depolarization between +40 and −80 mV in control and after application of 1 and 10 µM chloroquine. Dashed lines define zero current levels. B, Averaged steady-state I-V curves in the absence and presence of chloroquine at the indicated concentrations recorded in excised inside-out patches. C, Relative current-voltage relationships obtained for block of D172N Kir2.1 currents by chloroquine at the indicated concentrations. The continuous lines show fits with Woodhull equation, yielding an apparent Kd (at 0 mV) of 34 ± 11 µM with an apparent valence (z) of 1.6 ± 0.3 (n = 5 cells).